diff --git a/skimage/filter/rank/_crank16.pyx b/skimage/filter/rank/_crank16.pyx
index 87199e80..232d6812 100644
--- a/skimage/filter/rank/_crank16.pyx
+++ b/skimage/filter/rank/_crank16.pyx
@@ -4,7 +4,7 @@
 #cython: wraparound=False
 
 cimport numpy as cnp
-from libc.math cimport log2
+from libc.math cimport log
 from skimage.filter.rank._core16 cimport _core16
 
 
@@ -276,7 +276,7 @@ cdef inline dtype_t kernel_entropy(Py_ssize_t * histo, float pop,
         for i in range(maxbin):
             p = histo[i] / pop
             if p > 0:
-                e -= p * log2(p)
+                e -= p * log(p) / 0.6931471805599453
 
         return <dtype_t>e * 1000
     else:
diff --git a/skimage/filter/rank/_crank8.pyx b/skimage/filter/rank/_crank8.pyx
index c9e8b14f..cb7febac 100644
--- a/skimage/filter/rank/_crank8.pyx
+++ b/skimage/filter/rank/_crank8.pyx
@@ -4,7 +4,7 @@
 #cython: wraparound=False
 
 cimport numpy as cnp
-from libc.math cimport log2
+from libc.math cimport log
 from skimage.filter.rank._core8 cimport _core8
 
 
@@ -281,7 +281,7 @@ cdef inline dtype_t kernel_entropy(Py_ssize_t * histo, float pop,
         for i in range(256):
             p = histo[i] / pop
             if p > 0:
-                e -= p * log2(p)
+                e -= p * log(p) / 0.6931471805599453
 
         return <dtype_t>e * 10
     else:
diff --git a/skimage/filter/setup.py b/skimage/filter/setup.py
index 650a26a6..934d3f2e 100644
--- a/skimage/filter/setup.py
+++ b/skimage/filter/setup.py
@@ -29,31 +29,31 @@ def configuration(parent_package='', top_path=None):
         include_dirs=[get_numpy_include_dirs()])
     config.add_extension('_denoise_cy', sources=['_denoise_cy.c'],
         include_dirs=[get_numpy_include_dirs(), '../_shared'])
-    config.add_extension('rank/_core8', sources=['rank/_core8.c'],
+    config.add_extension('rank._core8', sources=['rank/_core8.c'],
         include_dirs=[get_numpy_include_dirs()])
-    config.add_extension('rank/_core16', sources=['rank/_core16.c'],
+    config.add_extension('rank._core16', sources=['rank/_core16.c'],
         include_dirs=[get_numpy_include_dirs()])
-    config.add_extension('rank/_crank8', sources=['rank/_crank8.c'],
+    config.add_extension('rank._crank8', sources=['rank/_crank8.c'],
         include_dirs=[get_numpy_include_dirs()])
     config.add_extension(
-        'rank/_crank8_percentiles', sources=['rank/_crank8_percentiles.c'],
+        'rank._crank8_percentiles', sources=['rank/_crank8_percentiles.c'],
         include_dirs=[get_numpy_include_dirs()])
-    config.add_extension('rank/_crank16', sources=['rank/_crank16.c'],
+    config.add_extension('rank._crank16', sources=['rank/_crank16.c'],
         include_dirs=[get_numpy_include_dirs()])
     config.add_extension(
-        'rank/_crank16_percentiles', sources=['rank/_crank16_percentiles.c'],
+        'rank._crank16_percentiles', sources=['rank/_crank16_percentiles.c'],
         include_dirs=[get_numpy_include_dirs()])
     config.add_extension(
-        'rank/_crank16_bilateral', sources=['rank/_crank16_bilateral.c'],
+        'rank._crank16_bilateral', sources=['rank/_crank16_bilateral.c'],
         include_dirs=[get_numpy_include_dirs()])
     config.add_extension(
-        'rank/rank', sources=['rank/rank.c'],
+        'rank.rank', sources=['rank/rank.c'],
         include_dirs=[get_numpy_include_dirs()])
     config.add_extension(
-        'rank/percentile_rank', sources=['rank/percentile_rank.c'],
+        'rank.percentile_rank', sources=['rank/percentile_rank.c'],
         include_dirs=[get_numpy_include_dirs()])
     config.add_extension(
-        'rank/bilateral_rank', sources=['rank/bilateral_rank.c'],
+        'rank.bilateral_rank', sources=['rank/bilateral_rank.c'],
         include_dirs=[get_numpy_include_dirs()])
 
     return config